The 21-year-old Spurs star scored twice as his side beat Antonio Conte's men 2-0 at White Harte Lane in January
Frank Lampard believes Chelsea have to find a way to stop Dele Alli if they are to beat Tottenham in their FA Cup semi-final on Saturday.
The last time the London rivals faced off against each other was in the Premier League and the 21-year-old well and truly stole the show.
Spurs ended Chelsea's attempt to make history with a 14th straight win in the league as Alli scored with his head in either half of the clash.
The former MK Dons man equalled his previous goals tally for the season by scoring his ninth and tenth on that day in January.
And since then has only gone from strength to strength, scoring six more times in the Premier League as Spurs continue to close the gap on Chelsea at the top of the table.
Lampard spoke to the BBC about his former side's upcoming clash with Tottenham, and picked the Spurs star out as the man who could cause the Blues problems.
"It is a big ask for Chelsea to nullify Alli completely on Saturday but it will be critical to the outcome of the game," said Lampard.
"For that to happen, it will be down to whoever plays in midfield for Chelsea – potentially N'Golo Kante and Nemanja Matic – to stop the service into him."
He added: "They will obviously have to deal with [Harry] Kane and what he is doing up top too, but behind him Alli will play a decisive role if the Blues allow him to."